At present, in a factory, a network for distributing a fluid, e.g. compressed air, is made essentially by plumbing, i.e. the pipes forming the network are put into place by hand (piping is cut to length, lengths are shaped on site as a function of local geometrical constraints, and coupling elements or branch connection elements are brazed, soldered, or glued to the lengths of piping). In some cases, use is also made of devices for coupling together lengths of tube by means of claws, as illustrated in document GB 2 117 072 which enables a certain amount of time to be saved. Modifying or extending an installation of that type requires the entire installation to be revised in order to add or remove such and such a branch connection. Even for small changes of the installation, e.g. increasing the diameter of a branch because of an increase in power demand on that line, it is necessary to undertake major work that keeps the installation out of operation for a long time.
The drawbacks of present installations and of their laying techniques can be remedied with connection means that enable a new installation to be assembled extremely quickly with the possibility of modifying easily its configuration, and the nature or the location of the functional elements that make it up.
Such connection means enable the pipe(s) making up the installation or the network to be subdivided into modular elements or lengths which are easily replaced or altered, said lengths being provided in a series of predetermined sizes and including no special end means for connection to the installation. The connection means are concentrated in a special element that is interposed between the end of a length and a functional member, which functional member comprises a rigid tubular body and may be no more than a union or a plug.
The term "endpiece" is used below to designate any cylindrical end of a rigid body provided internally with a fluid circulation channel and externally with coupling means (thread, collar, radial studs, camming elements, . . . ) for co-operating with corresponding coupling means of a tube coupling ring. The end is defined axially by a surface constituting an abutment for the tube to be connected.
To satisfy the needs for quick and easily modifiable connection, the means for connecting a tube to an endpiece are in the form of a cylindrical sleeve having an axial section which possesses means for fixing it to the endpiece and another axial section possessing retention means, e.g. claw connection means. In such a device, the tube does not penetrate into the endpiece, thereby enabling the link to be dismounted without it being necessary to extract the tube from the endpiece by an axial movement. It is thus possible to make networks of pipes using mutually adjacent lengths of tube with link pieces interposed between adjacent lengths (each link piece possessing an endpiece for each adjacent length). In addition to providing a link, this piece can perform other functions such as providing a branch connection, a cutoff function, a fluid pressure expansion function, purging, . . . When the layout of the network is to be changed using this type of connection, it is possible to extract at least one length of tube from the network laterally, i.e. without any need to perform an axial disengagement movement between the length of tube and the link pieces. Such axial movement would require the pieces to be dismounted to release them from the structure that carries them, since the network is generally fixed to said structure by said pieces.
This absence of axial engagement between the link pieces and the lengths of tube where they are connected together gives rise to points of mechanical weakness that are poor at withstanding the bending stresses to which the network can be subject, e.g. as a result of buckling forces due to the lengths of tube expanding. As a result, at the location of the link, the tube becomes ovalized and decentered, thereby harming the quality of the connection and of sealing at the connection.